Human pluripotent stem cells (hPSCs) win be crucial for the development of regenerative therapies, especially when autologous, specialized cells cannot be obtained in sufficient quantity. Despite great .promise, pluripotent embryonic stem (ES) cells have some recognized drawbacks. These include tumorigenicity and difficulty of histocompatibility matching. Other classes of hPSCs may overcome these limitations. In the agency-wide Program Announcement, amniotic fluid is noted specifically as a potential non-embryonic source for hPSCs. We recently described clonal human AFS cell lines and demonstrated that they are able to give rise to cell lineages that include representatives of each of the three embryonic germ layers. Others have described the use of defined genetic factors to reprogram somatic cells to an ES-like state, termed induced pluripotent stem (iPS) cells. We hypothesize that AFS cells represent a developmentally more advanced stage than ES and iPS cells, while nevertheless retaining a high degree of pluripotency. In particular, with support from preliminary data, we anticipate that AFS cells will not give rise to teratomas under conditions conducive to tumor formation by its and iPS cells, Therefore, critical comparison of genes expressed by AFS and ES or iPS cells should lead to significant insights into functions essential for pluripotency and also into those associated with teratoma formation. A confounding factor in such comparisons is that cell lines derived from different human beings are genetically diverse. In order to focus precisely on differences [unreadable] corresponding to developmental stage, we propose to compare matched pairs of AFS and iPS cells from the same individuals. This will be achieved by using defined factors to reprogram AFS cells to the more primitive ES-like state. (We refer to such reprogrammed cells iPS-AFS cells). In this revised version of our original R01 application we intend to hire two new employees from outside the University. A new junior post-doctoral fellow and a new junior technician.